Field of the Invention
The present invention relates to an X-ray detection signal processing device to which a signal from an X-ray detector is inputted, and which outputs a signal having a pulse height corresponding to energy of X-rays that are incident on the X-ray detector, and an X-ray analyzing apparatus using the X-ray detection signal processing device.
Description of Related Art
To date, for example, in X-ray fluorescence analysis, there is an X-ray detection signal processing device which amplifies, by a preamplifier, a signal from an X-ray detector (an output signal from an X-ray detector. Hereinafter, an output signal from each component will be similarly called), subjects the amplified signal to high-speed AD conversion by a high-speed AD converter, and smoothes the obtained signal by using a filter function of a signal processing section, thereby outputting a signal (a pulse height value), having a pulse height corresponding to energy (wavelength) of X-rays that are incident on the X-ray detector. The X-ray detection signal processing devices are classified into the following two conventional arts according to a type of the preamplifier (see paragraphs 0005, 0006 of Patent Document 1). In any of the conventional arts, two conditions that are a condition that a level of a signal from the preamplifier is within an unsaturated range, that is, within a range effective for the analysis, and a condition that the level of the signal is within a range for input to the high-speed AD converter, need to be satisfied in order to perform correct signal processing.
In an X-ray detection signal processing device 20 of the first conventional art, as shown in FIG. 4, a pulse reset type preamplifier 23 having a circuit 23a that includes a capacitor and a reset switch is used. In the preamplifier 23, as indicated by an output waveform in the upper right portion in FIG. 4, signals from the X-ray detector are amplified and then charged and piled up one by one in the capacitor. When the piled up level exceeds a predetermined upper limit value, a reset signal is outputted from a comparator 27 to the reset switch of the preamplifier 23, and the capacitor is discharged, and the preamplifier 23 is reset. The predetermined upper limit value in the comparator 27 is set so as to satisfy the above two conditions.
In an X-ray detection signal processing device 30 of the second conventional art, as shown in FIG. 5, a continuous reset type (also referred to as a tail pulse type, RC-coupled type, or the like) preamplifier 13 having a CR circuit 13a that includes a capacitor and a resistor, is used. In the preamplifier 13, as indicated by an output waveform in the upper left portion in FIG. 5, each signal from the X-ray detector is amplified and steeply rises, to charge the capacitor, similarly to the pulse reset type preamplifier 23 (FIG. 4). However, for each signal, the capacitor is discharged according to a time constant of the CR circuit 13a, to attenuate the charged level, unlike the pulse reset type preamplifier 23. For this characteristic, an approach, such as using of a comparator in which a threshold value is set, for satisfying the above two conditions, is not made except that a time constant is appropriately set in the CR circuit 13a. However, in general, the high-speed AD converter 14 has its own determination function and determines whether or not the level of a signal from the preamplifier 13 is within a range for input to the high-speed AD converter 14, and when the range for the input is exceeded, a signal outside the range is obtained and can be addressed without stopping the high-speed AD conversion.